Firefighters battle a massive fire at Country Club Plaza in Kansas City, Mo. Tuesday, Feb. 19, 2013. A car crashed into a gas main Tuesday evening in the upscale Kansas City shopping district, sparking a massive blaze that engulfed an entire block and caused multiple injuries, police said. Photo: AP/KCTV

KANSAS CITY, Mo. — Search crews at the site of a massive explosion that destroyed a popular Kansas City, Mo., restaurant recovered one body Wednesday, and the city’s mayor said there was no certainty the rubble wasn’t concealing other victims.

Mayor Sly James declined to say whether the body belonged to a man or a woman, though authorities have been looking for a woman who worked at JJ’s restaurant and was seen there before the Tuesday evening blast and reported missing afterward. They previously said she was the only person still unaccounted for following the explosion and fire.

But James said at a news conference that authorities can’t be “100 percent sure that we can account for every single person that may have been at JJ’s when the explosion occurred.”

“Since this started without a list of those in the building … those search and rescue people are out there going through the rubble and will continue to go through the rubble,” James said. “They will continue to investigate until weather shuts it down.”

Crews using flashlights, cadaver dogs and heavy equipment have been searching the site feverishly ahead of a major winter storm bearing down on the city. James said 15 people were injured in the blast. Six were still hospitalized Wednesday morning.

The blast occurred after a construction crew apparently struck a natural gas line. The explosion was felt for nearly a mile around the restaurant, shattering glass in nearby buildings and sending an ominous smoke plume above the city’s prized outdoor shopping district.

One of two people first feared to be missing was later found at a hospital. But the woman who worked at JJ’s was still missing, and James had stressed that finding her remained the primary focus of Wednesday’s efforts.

“We have a major storm coming in this evening,” James said. “We’re going to work diligently to get in (to the blast site) to get underneath that weather.”

Searchers were continuing their work at midday at JJs, a beloved fixture on the city’s culinary scene for more than 27 years. Locals knew it as a prime after-work stop, though the restaurant won a broader reputation after it consistently received high ratings from contributors to Zagat’s restaurant guides, both for its food and its list of hundreds of wines.

The blast happened at around 6 p.m. Tuesday, when the dinner crowd would have been filing into JJ’s and the many other restaurants in the upscale Country Club Plaza shopping and dining district.

Firefighters had received a call about 5:15 p.m. that a construction worker had hit a gas line near the restaurant, and they conferred with employees for Missouri Gas Energy, which supplies the area, Fire Chief Paul Berardi said. He said the cause of the gas leak has not yet been confirmed and is still under investigation.

It wasn’t clear Wednesday how hard firefighters or utility officials worked to evacuate the restaurant after gas was first noticed. Both James and Berardi said the fire department deferred to MGE since the utility would have more expertise in assessing the seriousness of the situation.

“It’s not a matter of deferring, it’s a matter of knowing a utility is involved. Fire department does not do gas, MGE does gas,” James said. “Everybody wants to know what happened, everybody wants to blame someone, everybody wants to know details. That’s not going to happen today.”

A construction project had been going on across a narrow, one-way street from JJ’s for seven years. The work had complicated access to the street-corner restaurant, and a server needed hospital treatment in 2006 after she was struck by a rock sent flying by blasting for excavation of the construction site.

It was not clear Wednesday whether the contractor MGE said had been doing underground work was connected to that construction project. MGE said it would issue a statement later Wednesday.

The Missouri Public Service Commission, which oversees utilities, has launched an investigation into the blast, dispatching five employees to the site. Commission Chairman Kevin Gunn said preliminary information indicates that gas pipelines had been marked — as required by law — before a contractor started doing work in the area. He says a gas leak appears to have occurred after a pipeline was hit.

Gunn said MGE followed state rules in promptly reporting the explosion. Investigators will look at whether it followed state rules in responding to the gas line leak reported beforehand. It could take up to six months before state regulators release a final report.

Dr. John Verstraete, who works at Plaza Physicians Group next door to JJ’s, told The Kansas City Star that several office employees smelled gas for several hours Tuesday afternoon. The smell grew stronger through the day, and a gas company employee entered the medical office just before 6 p.m. and recommended evacuating, he said.

William Borregard, 20, who lives with his sister and her fiancé in the apartment building nearest to JJ’s, said he had noticed a strange smell for weeks that had worsened in recent days. On Tuesday, they called the apartment manager.

“We said it’s very pungent, and you should come out here and check it out,” he said. “He came over and rapped on the door and said there’s nothing to worry about. Stay in your apartment. That was five minutes prior to the explosion. And as soon as he left the explosion happened.”